Build error for Python 3.13

[LecrisUT]

This was reported in Fedora upstream: https://bugzilla.redhat.com/show_bug.cgi?id=2254979

/builddir/build/BUILD/nlopt-2.7.1/redhat-linux-build/src/swig/CMakeFiles/nlopt_python.dir/nloptPYTHON_wrap.cxx: In function ‘double func_python(unsigned int, const double*, double*, void*)’:
/builddir/build/BUILD/nlopt-2.7.1/redhat-linux-build/src/swig/CMakeFiles/nlopt_python.dir/nloptPYTHON_wrap.cxx:5103:22: error: ‘PyEval_CallObject’ was not declared in this scope; did you mean ‘PyObject_CallObject’?
 5103 |   PyObject *result = PyEval_CallObject((PyObject *) f, arglist);
      |                      ^~~~~~~~~~~~~~~~~
      |                      PyObject_CallObject
/builddir/build/BUILD/nlopt-2.7.1/redhat-linux-build/src/swig/CMakeFiles/nlopt_python.dir/nloptPYTHON_wrap.cxx: In function ‘void mfunc_python(unsigned int, double*, unsigned int, const double*, double*, void*)’:
/builddir/build/BUILD/nlopt-2.7.1/redhat-linux-build/src/swig/CMakeFiles/nlopt_python.dir/nloptPYTHON_wrap.cxx:5140:19: error: ‘PyEval_CallObject’ was not declared in this scope; did you mean ‘PyObject_CallObject’?
 5140 |   PyObject *res = PyEval_CallObject((PyObject *) f, arglist);
      |                   ^~~~~~~~~~~~~~~~~
      |                   PyObject_CallObject

Basically the following needs to be guarded by python version macros:
https://github.com/stevengj/nlopt/blob/master/src/swig/nlopt-python.i#L154

[jschueller]

hello @stevengj,
I think it could be worth having a new release with this fix since python 3.13 will be released soon, what do you think ?
it will help downstream like Fedora, conda etc